#include<climits>
#include<algorithm>
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};
class Solution {
public:
    int minDepth(TreeNode* root) {
        if (root == nullptr) return 0;
        if (root->left == nullptr && root->right == nullptr) return 1;
        int left = INT_MAX, right = INT_MAX;

        if (root->left != nullptr) left = minDepth(root->left);
        if (root->right != nullptr) right = minDepth(root->right);
        return std::min( left,right)+1;
    }
};